AN INVESTIGATION OF A DIGITAL BEARING COMPUTER FOR A SMALL APERTURE RADIO DIRECTION FINDING SYSTEM

摘要

A smal1 aperture radio direction finding system such as a Watson-Watt system is subject to large bearing errors because of the wave interference effect of two waves. By contrast, a large aperture system such as a Wullenweber system exhibits smaller errors under corresponding conditions, This work attempts to develop a practicable means of obtaining accurate bearing information using a small aperture system in the presence of strong wave interference. The technique used is the time averaging of instantaneous bearings. Thus, bearing information may be obtained with a small aperture system by using information available over an extended period of time. The computation of the bearing may be carried out on-line by a small general purpose digital computer.nOne of the unique features of the digital bearing computer developed here is its capability to adapt to changing input signal conditions. The adaptive capability makes it possible to optimize the averaging process. The process allows estimates of the indicated bearings of both the primary and the inter¬fering waves and their relative strengths to be made.nA mathematical model for the relative phase between the two waves is evolved which is not unlike that of the real phase function. The model yields a regular progression of phase plus a random perturbing component. The only restriction placed upon the phase function is that its probability density function be essential uniform.nOn the basis of the model of the phase function and the equations describing the operation of a small aperture system, the Watson-Wyatt system is simulated on a general purpose digital computer, and the digital bearing computer is evalu¬ated. Further evaluation includes an experimental investigation.